Catheter with combined position and pressure sensing structures

ABSTRACT

A catheter is responsive to external and internal magnetic field generators for generating position data of the catheter position and pressure data to determine pressured exerted on a distal end of the catheter when engaged with tissue, with a reduced number of sensing coils and reduced number of sensing coil leads for minimizing lead breakage and failure. The catheter includes a distal section adapted for engagement with patient tissue, where the distal section has a proximal portion, a distal portion and a flexible joint with a resilient member adapted to allow axial displacement and angular deflection between the proximal and distal portions of the distal section. 
     The catheter may have three or less sensing coils with three or less leads, each transmitting signals between a respective sensing coil and the signal processor.

FIELD OF INVENTION

The present invention relates to catheters, particular catheters withlocation/orientation and pressure sensing capabilities.

BACKGROUND OF INVENTION

In some diagnostic and therapeutic techniques, a catheter is insertedinto a chamber of the heart and brought into contact with the innerheart wall. In such procedures, it is generally important that thedistal tip of the catheter engages the endocardium with sufficientpressure to ensure good contact. Excessive pressure, however, may causeundesired damage to the heart tissue and even perforation of the heartwall.

For example, in intracardiac radio-frequency (RF) ablation, a catheterhaving an electrode at its distal tip is inserted through the patient'svascular system into a chamber of the heart. The electrode is broughtinto contact with a site (or sites) on the endocardium, and electricalactivity in the heart chamber is detected by the electrode. Moreover, RFenergy may be applied through the catheter to the electrode in order toablate the heart tissue at the site. Proper contact between theelectrode and the endocardium is necessary in order to achieve thedesired diagnostic function and therapeutic effect of the catheter.

Catheters for mapping and/or ablation typically carry one or moremagnetic position sensors for generating signals that are used todetermine position coordinates of a distal portion of catheter. For thispurpose, magnetic field generators are driven to generate magneticfields in the vicinity of the patient. Typically, the field generatorscomprise coils, which are placed below the patient's torso at knownpositions external to the patient. These coils generate magnetic fieldsthat are sensed by the magnetic position sensor(s) carried in thecatheter. The sensor(s) generate electrical signals that are passed to asignal processor via leads that extend through the catheter.

For pressure sensing, a catheter typically carries a miniaturetransmitting coil and three sensing coils on opposing portions of aflexibly-jointed distal tip section. The transmitting coil is alignedwith the longitudinal axis of the catheter and three sensing coils arealso aligned with the longitudinal axis but positioned at an equaldistance from the transmitting coil, and at equally-spaced radialpositions about the longitudinal axis of the catheter. The miniaturetransmitting coil generates a magnetic field sensed by the three sensingcoils which generate signals representative of axial displacement andangular deflection between the opposing portions of the distal tipsection.

The axes of the sensing coils are parallel to the catheter axis (andthus to one another, when the joint is undeflected). Consequently, thesensing coils are configured to output strong signals in response to thefield generated by the miniature field generator. The signals varystrongly with the distances of the coils. Angular deflection of thedistal portion carrying the miniature field generator gives rise to adifferential change in the signals output by sensing coils, depending onthe direction and magnitude of deflection, since one or two of thesecoils move relatively closer to the field generator. Compressivedisplacement of the distal portion gives rise to an increase in thesignals from all of three sensing coils. Prior calibration of therelation between pressure on distal portion and movement of joint may beused by processor in translating the coil signals into terms ofpressure. By virtue of the combined sensing of displacement anddeflection, the sensors read the pressure correctly regardless ofwhether the electrode engages the endocardium head-on or at an angle.

With position sensing and pressure sensing, a conventional catheter maycarry six leads, one for each of the three position sensing coils andeach of the three pressure sensing coil, with each lead being a twistedpair of wires. Leads are time-consuming and expensive to manufacture andinstall. Moreover, the leads occupy space in the space-constrainedcatheter tip and are susceptible to breakage. A reduction in the numberof leads used in the catheter would provide a number of benefits,including reduced catheter production time, increased total catheteryield, and reduced production costs.

Accordingly, it is desirable to provide a catheter with combined orsimplified position and pressure sensing capabilities for reducing thenumber of sensor coils and hence the number of sensor coil leads.

SUMMARY OF THE INVENTION

The present invention is directed to a catheter responsive to externaland internal magnetic field generators for generating position data todetermine position of the catheter within a sensing volume of magneticfields and pressure data to determine pressured exerted on a distal endof the catheter when engaged with tissue, with a reduced number ofsensing coils and hence a reduced number of sensing coil leads forminimizing lead breakage and failure.

In one embodiment, the catheter includes a distal section adapted forengagement with patient tissue, where the distal section has a proximalportion, a distal portion and a flexible joint. Either of the proximalportion or the distal portion carries an internal magnetic fieldgenerator and the other of the proximal portion or the distal portioncarries a plurality of sensing coils, each mutually orthogonal to eachother and sensitive both to the internal magnetic field generator forgenerating signals representative of pressure exerted on the distalsection and to a plurality of external magnetic field generators drivenby a catheterization system for generating signals representative ofposition of the distal section, wherein each coil has a dedicated leadadapted to transmit both the signals representative of pressure andposition to a signal processor provided in the catheterization system.

In one embodiment, the flexible joint includes a resilient memberadapted to allow axial displacement and angular deflection between theproximal and distal portions of the distal section.

In one embodiment, the catheter has three or less sensing coils withthree or less leads, each transmitting signals between a respectivesensing coil and the signal processor.

In one embodiment, the sensing coils consist of two elliptical sensorsand one cylindrical (namely, longer and narrower) sensor. In a moredetailed embodiment, the internal field generator is aligned with a Zaxis, one elliptical sensor is aligned with an X axis, anotherelliptical sensor is aligned with a Y axis, and the cylindrical sensoris aligned with the Z axis.

In one embodiment, each magnetic field is distinguishable by frequency,phase and/or time.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic, pictorial illustration of a catheter-basedmedical system, in accordance with an embodiment of the presentinvention.

FIG. 2 is a side view of a catheter for use with the system of FIG. 1,in accordance with an embodiment of the present invention.

FIG. 3 is a schematic, cutaway view showing details of the distalsection of the catheter of FIG. 2.

FIG. 4 is a schematic detail view showing the distal section of FIG. 3in contact with endocardial tissue.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a system and catheter for cardiaccatheterization, wherein the catheter has a sensing assembly thatprovides signals representative of both position of the catheter andpressure exerted on a distal section of the catheter when it engagestissue. Compared to conventional position sensing assemblies andpressure sensing assemblies, the sensing assembly of the catheteradvantageously employs a reduced number of sensor coils and hence areduced number of sensor coil leads for a simplified catheter structurethat minimizes the risk of damaged or broken leads.

FIG. 1 is a schematic, pictorial illustration of a conventional system20 for cardiac catheterization as known in the art. System 20 may bebased, for example, on the CARTO™ system, produced by Biosense WebsterInc. (Diamond Bar, Calif.). This system comprises an invasive probe inthe form of a catheter 28 and a control console 34. In the embodimentdescribed hereinbelow, it is assumed that catheter 28 is used inablating endocardial tissue, as is known in the art. Alternatively, thecatheter may be used, mutatis mutandis, for other therapeutic and/ordiagnostic purposes in the heart or in other body organs. As shown inFIG. 2, the catheter 28 comprises an elongated catheter body 11, adeflectable intermediate section 12, a distal section 13 carrying atleast a tip electrode 15 on its distal tip end 30, and a control handle16.

An operator 26, such as a cardiologist, inserts catheter 28 through thevascular system of a patient 24 so that a distal section 13 of thecatheter enters a chamber of the patient's heart 22. The operatoradvances the catheter so that a distal tip 30 of the catheter engagesendocardial tissue 70 at a desired location or locations. Catheter 28 isconnected by a suitable connector at its proximal end to console 34. Theconsole may comprise a radio frequency (RF) generator, which supplieshigh-frequency electrical energy via the catheter for ablating tissue inthe heart at the locations engaged by the distal section 13.Alternatively or additionally, the catheter and system may be configuredto perform other therapeutic and diagnostic procedures that are known inthe art.

Console 34 uses magnetic sensing to determine data, including (i)position coordinates of the distal section 13 in the heart and (ii) itsaxial displacement and angular deflection due to pressure from contactwith endocardial tissue 70. For the purpose of generating position dataor coordinates, a driver circuit 38 in console 34 drives externalmagnetic field generators, for example, F1, F2 and F3, to generatemagnetic fields in the vicinity of the body of patient 24 and define anexternal frame of reference The generators F1, F2 and F3 are comprisedof coils, which are placed below the patient's torso at known positionsexternal to the patient. These coils generate magnetic fields within thepatient's body in a predefined working volume that contains heart 22.

For the purpose of generating pressure data, including axialdisplacement and angular deflection of the distal section 13 of thecatheter 28, the driver circuit 38 in console 34 drives an internalminiature magnetic field generator MF housed in a distal portion 13D ofthe tip section 13, as shown in FIG. 3. In the disclosed embodiment, thefield generator MF comprises a coil whose axis is aligned with the Zaxis defining a longitudinal axis 25 of the catheter.

With reference to FIGS. 1 and 3, a sensor assembly 17 within distalsection 13 of catheter 128 is advantageously responsive to both of thefield generators F1, F2, F3 and the miniature field generator MF. Thatis, the sensor assembly 17 generates electrical signals in response tothe magnetic fields generated by the field generators F1, F2 and F3 andthe miniature field generator MF.

For detecting and measuring pressure, the distal section 13 has aproximal portion 13P and a distal portion 13D which are connected toeach other by a flexible and elastic joint 54 which may be constructedof any suitable material(s) with the desired flexibility and strength.The resilient joint 54 permits a limited range of relative movementbetween the portions 13P and 13D in response to forces exerted on thedistal section 13. Such forces are encountered when the distal tip end30 is pressed against the endocardium during an ablation procedure. Asshown in FIG. 4, the distal end 30 of catheter 28 is in contact withendocardium 70 of heart 22, in accordance with an embodiment of thepresent invention. Pressure exerted by the distal tip end 30 against theendocardium deforms the endocardial tissue slightly, so that the tipelectrode 15 contacts the tissue over a relatively large area. Since theelectrode engages the endocardium at an angle, rather than head-on, thedistal portion 13D bends at joint 54 relative to the proximal portion13P. The bend facilitates optimal contact between the electrode 15 andthe endocardial tissue 70.

As shown in FIG. 3, the joint 54 comprises an outer tubing 56 which maybe the outer tubing 55 of the distal section 13 which is constructed ofa flexible, insulating material, such as Celcon®, Teflon®, orheat-resistant polyurethane. Or, the tubing 56 may be of a materialspecially adapted to permit unimpeded bending and compression of thejoint. (This material is cut away in FIG. 3 in order to expose theinternal structure of the catheter.) The distal section 13D is typicallyrelatively rigid, by comparison with the remainder of the catheter.

The joint 54 further comprises a resilient coupling member 60, such as acoil spring, or a tubular piece of an elastic material with a helicalcut along a portion of its length. For example, the coupling member maycomprise a polymer, such as silicone, polyurethane, or other plastics,or a superelastic alloy, such as nickel titanium (Nitinol). The helicalcut causes the tubular piece to behave like a spring in response toforces exerted on distal portion 13D. Further details regarding thefabrication and characteristics of this sort of coupling member arepresented in U.S. patent application Ser. No. 12/134,592, filed Jun. 6,2008, which is assigned to the assignee of the present patentapplication and whose disclosure is incorporated herein by reference.Alternatively, the coupling member may comprise any other suitable sortof resilient component with the desired flexibility and strengthcharacteristics.

The stiffness of the coupling member 60 determines the range of relativemovement between distal portions 13P and 13D in response to forcesexerted on the distal portion 13D. Such forces are encountered when thedistal tip end 30 is pressed against the endocardium during a mappingand/or ablation procedure. The desired pressure for good electricalcontact between the distal portion 13D and the endocardium duringablation is on the order of 20-30 grams. The coupling member 60 isconfigured to permit axial displacement (i.e., lateral movement alongthe longitudinal axis 25 of catheter 28) and angular deflection of thedistal portion 13D in proportion to the pressure on the distal tip end30. Measurement of the displacement and deflection gives an indicationof the pressure and thus helps to ensure that the correct pressure isapplied during ablation.

The magnetic field sensor assembly 17 is housed in the proximal portion113P as shown in FIG. 3. In the illustrated embodiment, the sensor 17includes three miniature sensor coils SCx, SCy and SCz wound on aircoils. The coils have generally mutually orthogonal axes, with coil SCzaligned with the longitudinal axis 25 of the catheter, which is referredto as the Z axis, the coil SCx aligned with the X axis and the coil SCyaligned with the Y axis of an (X,Y,Z) coordinate system.

The three coils are all located in the same axial section at differentazimuthal angles about the catheter longitudinal or Z axis, where anaxial plane is defined herein as a plane perpendicular to the catheterlongitudinal or Z axis and an axial section is defined herein as beingcontained within two axial planes of the catheter. For example, thethree coils may be spaced azimuthally 120 degrees apart at the sameradial distance from the axis. The three coils SCi may be a combinationof position sensors and pressure sensors, such as those described inU.S. Pat. No. 6,690,963 and U.S. Publication No. 20090138007, the entiredisclosures of which are incorporated herein by reference. In theillustrated embodiment, the sensor coil SCz is configured as a positionsensor, and the sensor coils SCx and SCy are configured as pressuresensors.

Electromagnetic or magnetic fields are transmitted between the fieldgenerators F1, F2, F3 placed under the patient's torso and the sensorcoils SCz, SCx and SCy housed in the catheter 28 for detecting positionof the catheter. The magnetic fields created by the field generators F1,F2 and F3 cause the coils SCz, SCx and SCy to generate electricalsignals, with amplitudes that are indicative of the position of thesensor assembly 17 relative to the fixed frame of reference of fieldgenerators F1, F2 and F3. In one embodiment, the three field generatorsF1, F2 and F3 generates a magnetic field composed of threedifferently-oriented field components. Each of these field components issensed by each sensor coil SCz, SCx and SCy, each of which produces asignal composed of three components.

As shown in FIG. 1, the console 34 includes a signal processor 36 thatprocesses these signals in order to determine the position coordinatesof the distal section 13, typically including both location andorientation coordinates. This method of position sensing is implementedin the above-mentioned CARTO system and is described in detail in U.S.Pat. Nos. 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612 and6,332,089, in PCT Patent Publication WO 96/05768, and in U.S. PatentApplication Publications 2002/0065455 A1, 2003/0120150 A1 and2004/0068178 A1, all of whose disclosures are incorporated herein byreference.

For detecting and measuring pressure exerted on the distal portion 13D,an additional electromagnetic or magnetic field is transmitted by thefield generator MF in the distal portion 13D and sensed by the sensorcoils SCz, SCx and SCy located in the proximal portion 13D of the distalsection 13. Axial displacement and/or angular deflection of the distalportion 13D relative to the proximal portion 13P gives rise to adifferential change in the signal outputs by the coils SCz, SCx and SCy,depending on the direction and magnitude of deflection, since one or twoof these coils move relatively closer to the field generator MF.Compressive displacement of the distal portion 13D gives rise to anincrease in the signals from each of the coils SCz, SCx and SCy. Changesin the sensing of the magnetic field by generator MF causes the coilsSCz, SCx and SCy to generate electrical signals, with amplitudes thatare indicative of such axial displacement and/or angular deflection.

It is understood that while the coils SCx and SCy are orthogonal to andnot aligned with the axis of the miniature field generator MF, themagnetic dipole field lines surrounding the field generator MF allowdetection by the orthogonal coils SCx and SCy. While the coils SCx andSCy may sense a relatively weaker magnetic field by field generator MFcompared to the coil SCz because of their respective orientationrelative to the field generator MF, there is sufficient sensitivity forpurposes of detecting and measuring pressure applied to the distalsection 13. Moreover, the signal processor 36 can be calibrated tocompensate for this discrepancy, as understood by one of ordinary skillin the art.

Because the coil of the generator MF in the distal portion 13D isradially symmetrical, it is well suited for on-axis alignment with thelongitudinal axis 25 of the catheter. However, it is understood that thecoil may also be off-axis as desired or appropriate, with the furtherunderstanding that tilting the coil off-axis will both improve certaincoil(s) and degrade other coil(s) of mutually orthogonal SCx, SCy andSCz sensors.

It is also understood that the coils of the sensors SCx, SCy and SCz maybe of any suitable size and shape provided they conform to packagingconstraints within the distal section 13 of alignment and/or mutualorthogonality. Conventional pressure sensors tend to be cylindrical(longer and narrower) because of Z axis alignment with the generator MFwithin the distal section, whereas conventional X and Y position sensorstend to be more elliptical so as to maintain mutual orthogonality withthe Z position sensor and conformity with the packaging constraints ofthe distal section. In the disclosed embodiment of the presentinvention, the sensor SCz configured more as a conventional pressuresensor may be more cylindrical, whereas the sensors SCx and SCyconfigured more as conventional position sensors may be more elliptical.

As shown in FIG. 3, lead 62 extends between the coil SCz and the signalprocessor 36 to pass signals from the coil SCz to the signal processor.Lead 63 extends between the coil SCx and the signal processor 36 to passsignals from the coil SCx to the signal processor. Lead 64 extendsbetween the coil SCy and the signal processor 36 to pass signals fromthe coil SCy to the single processor.

Accordingly, the catheter 28 has three leads, namely, leads 62, 63 and64 for position and pressure sensing compared to the typical five or sixleads of a conventional catheter with position and pressure sensing.Each lead is time-consuming and expensive to manufacture and assemble ina catheter. Moreover, leads occupy space in a space-constrainedcatheter. Leads are also susceptible to breakage. Having a reducednumber of sensors and hence leads, the catheter 28 provides a number ofbenefits, including reduced catheter production time, increased totalcatheter yield, and reduced production costs.

The magnetic fields generated by each field generator F1, F2, F3 and MFare distinguishable with regard to different parameters, includingfrequency, phase and/or time, and the signals generated by each sensorcoil SCz, SCx and SCy from measuring the magnetic field flux resultingfrom these distinguishable magnetic fields are similarlydistinguishable. Frequency, phase and/or time multiplexing is applied asappropriate or desired. For example, the current to pressure-sensingfield generator MF may be generated at a selected frequency in the rangebetween about 16 kHz and 25 kHz, while position field generators F1, F2and F3 are driven at different frequencies.

The signal processor 36 processes these signals in order to determinedata, including (i) the position coordinates of the distal section 13,typically including both location and orientation coordinates, and (ii)axial displacement and angular deflection of the distal section 13. Thesignal processor 36 may comprise a general-purpose computer, withsuitable front end and interface circuits for receiving signals fromcatheter 28 and controlling the other components of console 34. Theprocessor may be programmed in software to carry out the functions thatare described herein. The software may be downloaded to console 34 inelectronic form, over a network, for example, or it may be provided ontangible media, such as optical, magnetic or electronic memory media.Alternatively, some or all of the functions of processor 36 may becarried out by dedicated or programmable digital hardware components.Based on the signals received from the catheter and other components ofsystem 20, processor 36 drives a display 42 to give operator 26 visualfeedback regarding the position of distal end 30 in the patient's body,as well as axial displacement and angular deflection of the distal tipof the catheter, and status information and guidance regarding theprocedure that is in progress.

The processor 36 receives these signals via the leads 62, 63 and 64extending through catheter 28, and processes the signals in order toderive the location and orientation coordinates of the distal section 13in this fixed frame of reference, and to derive pressure information,including axial displacement and angular deflection of the distalsection. The disposition of the coils SCz, SCx and SCy and pressureexerted on the distal portion 13D of the distal section 13 can becalculated from the characteristics of the fields, such as strength anddirection, as detected by the coils. Thus, the field generators F1, F2,F3 and MF and the sensing coils SCz, SCx and SCy cooperatively define aplurality of transmitter-receiver pairs, including (F1/SCz), (F1/SCx),(F1/SCy), (F2/SCz), (F2/SCx), (F2/SCy), (F3/SCz), (F3/SCx), (F3/SCy),(MF/SCz), (MF/SCx), and (MF/SCy). Each such pair includes one fieldgenerator and a different coil as elements of the pair, with each coildisposed at a different position or orientation from the other coils. Bydetecting the characteristics of field transmissions between theelements of the various pairs, the system can deduce informationrelating to the disposition of the distal section 13 in the externalframe of reference as defined by the field generators F1, F2, and F3 andinformation relating to pressure exerted on the distal section MF assensed within the magnetic field generated by field generator MF. Theposition information can include the position of the distal section 13,the orientation of the distal section 13, or both. As understood by oneof ordinary skill in the art, the calculation of position informationrelies upon the field generators F1, F2 and F3 being positioned in knownpositions and orientations relative to one another, and the calculationof pressure based on axial displacement and angular deflection reliesupon the field generator MF and the sensing coils SCz, SCx and SCy beingin known positions and orientations relative to each other.

The field generating coils F1, F2, F3 and MF are one type of magnetictransducer that may be used in embodiments of the present invention. A“magnetic transducer,” in the context of the present patent applicationand in the claims, means a device that generates a magnetic field inresponse to an applied electrical current and/or outputs an electricalsignal in response to an applied magnetic field. Although theembodiments described herein use coils as magnetic transducers, othertypes of magnetic transducers may be used in alternative embodiments, aswill be apparent to those skilled in the art.

Various other configurations of the coils in the sensing assemblies mayalso be used, in addition to the configuration shown and describedabove. For example, the positions of the field generator MF and thecoils SCz, SCx and SCy may be reversed, so that that field generatorcoil MF is in the proximal portion 13D, proximal of joint 54, and thesensor coils are in the distal portion 13D. As another alternative,coils SCz, SCx and SCy may be driven as field generators (using time-and/or frequency-multiplexing to distinguish the fields), while fieldgenerator coil MF serves as the sensor. The sizes and shapes of thetransmitting and sensing coils in FIG. 3 are shown only by way ofexample, and larger or smaller numbers of coils may similarly be used,in various different positions, so long as one of the assembliescomprises at least two coils, in different radial positions, to allowdifferential measurement of joint deflection.

The preceding description has been presented with reference to certainexemplary embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes to the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention. It is understood that the drawings are not necessarilyto scale. Accordingly, the foregoing description should not be read aspertaining only to the precise structures described and illustrated inthe accompanying drawings. Rather, it should be read as consistent withand as support for the following claims which are to have their fullestand fairest scope.

What is claimed is:
 1. A catheter for use with a catheterization systemhaving a plurality of magnetic field generators, each generating aposition-data magnetic field, comprising: a flexible tubing; and adistal section adapted for engagement with patient tissue, the distalsection having: a proximal portion, a distal portion and a flexiblejoint between the proximal portion and the distal portion; a distalsection magnetic field generator positioned in one of the proximal anddistal portions, the distal section magnetic field adapted to generate apressure-data magnetic field; a plurality of sensing coils positioned inthe other of the proximal and distal portions; wherein at least onesensing coil is configured to sense each position-data magnetic fieldand each pressure-data magnetic field and generate signalsrepresentative of data relating to position of the distal section anddata relating to pressure exerted on the distal section when engagedwith the patient tissue; and wherein the at least one sensing coil has arespective lead connected thereto configured to transmit signals forsignal processing.
 2. The catheter of claim 1, wherein the flexiblejoint includes a resilient member adapted to allow axial displacementand angular deflection between the proximal and distal portions of thedistal section.
 3. The catheter of claim 1, wherein the system includesa signal processor and the respective lead carries the signalsrepresentative of the data relating to position and pressure to thesignal processor.
 4. The catheter of claim 1, wherein the plurality ofsensing coils is three or less.
 5. The catheter of claim 1, wherein eachof the sensing coils has only one respective lead.
 6. The catheter ofclaim 1, wherein the sensing coils consist of two elliptical sensors andone cylindrical sensor.
 7. The catheter of claim 6, wherein oneelliptical sensor is aligned with an X axis, another elliptical sensoris aligned with a Y axis, and the cylindrical sensor is aligned with theZ axis.
 8. The catheter of claim 1, wherein the distal section magneticfield generator is a transmitting coil axially aligned with alongitudinal axis of the catheter.
 9. The catheter of claim 8, wherein afirst sensing coil is axially aligned with the transmitting coil and asecond and a third sensing coils are generally orthogonal to the firstsensing coils and to each other.
 10. The catheter of claim 9, whereineach of the sensing coils senses each position-data magnetic field andthe pressure-data magnetic field to generate signals representative of aposition of the distal section and a pressure exerted on the distalsection when engaged with the patient tissue.
 11. A catheter for usewith a catheterization system having at least three magnetic fieldgenerators, each generating a position-data magnetic field, comprising:a flexible tubing; and a distal section adapted for engagement withpatient tissue, the distal section having: a proximal portion, a distalportion and a flexible joint between the proximal portion and the distalportion; a distal section magnetic field generator positioned in thedistal portion, the distal section magnetic field configured to generatea pressure-data magnetic field; at least three mutually-orthogonalsensing coils positioned in the proximal portion; wherein each sensingcoil is configured to sense each position-data magnetic field and eachpressure-data magnetic field and generate signals representative of datarelating to position of the distal section and data relating to pressureexerted on the distal section when engaged with the patient tissue; andwherein each sensing coil has a respective lead connected theretoconfigured to transmit signals for signal processing.
 12. The catheterof claim 10, wherein the flexible joint includes a resilient memberadapted to allow axial displacement and angular deflection between theproximal and distal portions of the distal section.
 13. The catheter ofclaim 10, wherein the system includes a signal processor and therespective lead carries the signals representative of the data relatingto position and pressure to the signal processor.
 14. The catheter ofclaim 1, wherein the three sensing coils consist of two ellipticalsensors and one cylindrical sensor.
 15. The catheter of claim 14,wherein one elliptical sensor is aligned with an X axis, anotherelliptical sensor is aligned with a Y-axis, and the cylindrical sensoris aligned with the Z axis.
 16. The catheter of claim 13, wherein thedata relating to pressure includes data relating to axial displacementand angular deflection between the proximal and distal portions of thedistal section.
 17. The catheter of claim 11, wherein the distal sectionmagnetic field generator is a transmitting coil axially aligned with alongitudinal axis of the catheter.
 18. The catheter of claim 17, whereina first sensing coil is axially aligned with the transmitting coil and asecond and a third sensing coils are generally orthogonal to the firstsensing coils and to each other.
 19. The catheter of claim 18, whereineach of the sensing coils senses each position-data magnetic field andthe pressure-data magnetic field to generate signals representative ofdata relating to position of the distal section and data relating topressure exerted on the distal section when engaged with the patienttissue.
 20. The catheter of claim 11, wherein each magnetic field isdistinguishable by one or more of the group consisting of frequency,phase and time.